Nickel electroplating bath and process



United States Patent ()flice 3,251,772 Patented July 19, 1965 3,261,772 NICKEL ELECTROPLATING BATH AND PROCESS Harry A. H. Ericson, Warby, Fittja, Sweden, assignor to Firma Sture Granberger, Bochum, Germany No Drawing. Filed May 14, 1964, Ser. No. 367,592 Claims priority, application Sweden, Dec. 17, 1963, 14,058/ 63 32 Claims. (Cl. 204-49) The present invention relates to the electro-deposition of nickel from an aqueous acidic nickel plating bath and, more particularly, to the production of bright and level electrodeposits of good ductility and adherence.

It is known to modify nickel electroplating baths with brightening agents as Well as with agents to improve leveling effects. However, it has been observed that during the electroplating process when the bath contains conventional brightening and leveling agents, hydrogen is evolved at the cathode in quantities suflicient to produce deleterious effects which result in reduced corrosion protection for the base metal.

It is, therefore, an object of this invention to provide an electroplating process whereby bright, level and adherent nickel electrodeposits can be obtained free from the disadvantageous effects of hydrogen evolution at the cathode which substantially reduces the corrosion protection desired for the base metal.

Another object of this invention is to provide an additive for nickel plating baths from which bright, level, ductile and adherent nickel deposits may be obtained.

A further object of this invention is to provide an additive for nickel plating baths which is a cathode depolarizer and a process wherein the additive is employed to reduce the evolution of hydrogen at the cathode so as to produce on the base metal a porous free deposit having increased corrosion protection characteristics.

It is still another object of this invention to provide a nickel plating bath incorporating the novel cathode depolarizer of this invention, together with a brightener of the first class to produce a coating possessing mirror bright deposits of high luster.

Yet another object of this invention is to provide a nickel plating bath incorporating an imidazol type brightener as disclosed in my copending application Serial No. 239,329, filed November 21, 1962, now US. Patent 3,130,135, to produce a coating possessing good ductility and improved corrosion resistance properties by a more economical method.

With the foregoing objects in View, as Well as others which will become apparent as the description proceeds, the invention consists in the novel plating process, the novel additive and bath compositions which will be described in certain illustrative examples hereinafter and which will then be more particularly pointed out in the appended claims.

It has now proved possible to produce nickel coatings with high brightness and good ductility by employing nickel plating baths containing a brightener having the following structural formula:

wherein R is selected from the group consisting of alkenyl, alkynyl, alkenoyl or alkynoyl radicals having 1 to 6 carbon atoms; R is selected from the group consisting of hydrogen, aliphatic, alicyclic or aromatic groups; R, is an aliphatic bridge containing from 1 to carbon atoms and R is selected from the group consisting of hydrogen and alkali metal. The novel brightener of this invention is generally used in amounts between 0.001 and 5 millimoles per liter of bath solution and preferably between 0.001 to 1 millimole per liter of solution.

In general, the process of the invention involves operating a bath at conventional nickel plating temperatures ranging from about 30 C. to as high as C. with a range of 4065 C. being especially desirable. The pH of the plating bath, as determined electrochemically, can range from around 1.5 to 5.0 with 3.0 to 5.0 being found especially suitable in the majority of cases. Practically all baths for electroplating nickel contain nickel sulfate, a chloride, usually nickel chloride, a buffering agent, usually boric acid and a wetting agent. Such types of baths include the well-known Watts-type bath and high chloride type bath. The Watts bath solution to which the novel brightener of this invention can be added typically comprises around 300 grams per liter of nickel sulfate, 60 grams per liter of nickel chloride and 40 grams per liter of boric acid. The foregoing bath composition and specified operating conditions are not critical in the basic Watts bath solution and the particular temperature and pH thereof may vary within the indicated ranges without adverse effects. Considerable latitude is also permissible in respect to the types and concentrations of the nickel salts employed, for instance, as the source of nickel, a combination of nickel fluoborate with nickel sulfate and nickel chloride, or a combination of nickel fluoborate with nickel chloride can be used.

In another embodiment of this invention the nickel plating bath solution can contain, in addition to the novel brightener of this invention, a brightener of the first class which is, preferably, an aromatic sulfur compound such as p-toluene 'sulfonamide, oabenzoyl :sulfimide, benzene sulfonarnide, naphthalene sulfonic acid, benzene sulphonic acid, Z-butyne, 1,4-disulphonic acid, allyl sulphonic acid together with Z-butyne, 1,4-dioxyethanesulphonic acid or sodium saccharate. Generally the aromatic sulfur compound will be present in amounts ranging from 0.1 to 30 grams per liter of solution. Additionally, if the bath is air agitated, comparable brightening effects are obtained with a substantially less brightener concentration. In this latter instance the novel brightener of the invention is generally employed in amounts ranging between 0.025 to 2.5 millimoles per liter of solution while the brightener of the first class advantageously is employed in amounts ranging from 0.05 to 15 grams per liter of solution. A mirror bright deposit of high luster is obtained when using this combination of brighteners.

Especially advantageous results are achieved in yet another embodiment of the invention wherein the novel brighteners of this invention are employed with an imidazol compound disclosed in my copending application Serial No. 239,329, filed November 21, 1962, and incorporated herein by reference, having the formula wherein R is selected from the group consisting of hydrogen and -AR A being an aliphatic bridge and R being selected from the group consisting of unsaturated and saturated aliphatic and cyclic radicals and aromatic radicals; wherein R and R are selected from the group consisting of hydrogen, aliphatic and cyclic, saturated and unsaturated hydrocarbon radicals, and wherein R is selected from the group consisting of hydrogen and A-R A being an aliphatic bridge and R being se lected from the group consisting of aliphatic and cyclic, saturated and unsaturated hydrocarbon radicals and aliphatic radicals bearing at least one amino group, and alkoxy groups; at least one of R and R being an unsaturated radical. Imidazol compounds representative of the aforedescri'bed compounds are, for instance, 3-pr0- 3 pynyl-amino-ethyl-imidazol, 3-propynyl-imidazole, 2-propynyl-3-(beta hydroxyethyl)-imidazol, 2-propenyl-imidazol and 2-propynyl-3-diethylenediamine-imidazol. Generally, the novel brightener of this invention is employed in synergistic amounts ranging from about 0.1 to 0.5 millimole per liter of solution while the imidazol compound is effectively used in amounts from about 0.005 to 0.01 millimole per liter of solution although an amount of the novel brightener of this invention ranging from 0.05 to 5 millimoles per liter and an amount of the imidazol ranging from 0.001 to 1 millimole per liter can be eifectively used. This combination of brightener additives results in a more economical deposition of nickel coating and results in the reduction of break-down product formation which in turn results in longer cycles between filtering and/or purification of the nickel plating bath solution.

While various wetting agents can be used in association with the novel plating bath compositions of this invention such as sodium lauryl sulfate, sodium lauryl ether sulfate and 7-ethyl-2-methyl-4 undecanol, it has been found that particularly advantageous results are produced when a wetting agent is employed having, preferably, the following formula and used in amounts of about 0.5 to 5 g./l.

wherein R is an alkanoyl group having 8 to 10 carbon atoms, R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals, R is and R is selected from the group consisting of hydrogen and alkali metals. Representative wetting agents of this type are sodium octanoyl methyl taurate, potassium nonanoyl methyl taurate, sodium decanoyl methyl taurate, sodium octanoyl cyclohexyl taurate, sodium nonanoyl methyl phenyl taurate, sodium decanoyl phenyl taurate, sodium octanoyl cyclopropyl taurate,. octanoyl hexyl amino propylene sulfonic acid, sodium salt of decanoyl cyclobutyl amino butylene sulfonic acid, and octanoyl tauric acid.

Additionally where heavily contaminated nickel plating baths are encountered, it has been found advantageous to incorporate therein oleoyl methyl taurate as a wetting or surface active agent. This wetting agent produces a billowy foam. Generally this type of wetting agent is employed in situations utilizing mechanical rather than air agitation means.

To reduce the sensitivity of the novel nickel plating bath compositions of this invention with respect to metallie and/ or organic contaminants, a sequestering agent having the following formula may be employed,

wherein R is an alkanoyl radical containing 1 to 6 carbon atoms, R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals, R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consisting of hydrogen and alkali metals. Representative sequestering agents of this type are sodium methyl formyl taurate, potassium methyl glyoxyl taurate, sodium methyl heptahydroxyhexanoyl taurate, sodium formyl cyclohexyl taurate, sodium glyoxyl methyl phenyl taurate, sodium butanoyl cyclopropyl taurate, sodium hexanoyl hexyl taurate, pentanoyl hexyl amino propylene sulfonic acid, sodium salt of formyl cyclobutylamino butylene :sulfonic acid and heptahydroxyhexanoyl tauric acid. Usually the sequestering agent is employed in amounts of about 0.1 to 5 grams per liter of bath solution.

For the purpose of giving those skilled in the art a better understanding of the invention, illustrative examples are given. In the examples, an aqueous acidic nickelcontaining bath was made up with the specified components. Electro-deposition was carried out by passing electric current through an electric circuit comprising an anode and a sheet metal or rod cathode, both immersed in the bath. The baths were agitated, usually by a moving cathode although in certain instances air agitation was employed. The examples utilizing the novel brighteners of this invention resulted in a nickel coating with improved leveling effects and corrosion resistance properties. In the examples employing, additionally, a brightener of the first class, i.e. an aromatic sulfur compound, the resulting sulfur-containing nickel coating also exhibited mirror bright characteristics as well as stress-free properties. High brightness and improved ductility properties were achieved in those examples where in combination with the novel brighteners of this invention, an imidazol compound was employed.

In the examples, the following standard Watts-type bath was used as a base solution:

Nickel sulfate 'g./l 300 Nickel chloride g./l 60 Boric acid g./l 40 pH 3.05.0 Temperature C 4065 Current density am peres/dmflu 1-20 Example 1 Sodium propargyl methyl taurate mmol/l 2 Example 2 Sodium propargyl methyl taurate mmol/l" 2 Sodium naphthalene tri-sulfonic acid m.mol/l '10 Sodium methyl oleoyl taurate g./l 0.1

Example 3 Sodium propargyl cyclohexyl taurate mmol/1 1.0 Sodium saccharate 'g./1 1.5 Sodium octanoyl methyl taurate (air agitated g./l 0.5

Example 4 Sodium propenyl methyil taurate mmol/l 2.0 Sodium sacch-arate g./l 1.5 Sodium heptahydroxyhexanoyl taurate (air agitated) g./l 2.0

Example 5 Sodium propenylmethyl taurate mmol/l 0.5 Sodium saccharate 'g./l 1.5 P'ropargylaminoethylene imidazol *mmol/l 0.01 Sodium octanoylmethyl taurate (air agitated) g./l 0.2

Example 6 Sodium hydroxy butynyl taurate I1'1II10ll/l 1.0 Sodium saccharate g./l 1.5 Z-propenyl-Lamino i-midazol mmol/l 0.01 Sodium octanoylmethyl taurate (air agitated) I -g./l 0.2

Example 7 Sodium propargylmethyl taurate mmol/l" 1.0 Sodium saccharate g./ 1.5 Proparagylaminoethylene imidazol mmol/l 0.001 Sodium methy l oleoyl taurate g./l 0.2

Example 8 Sodium vinyl methylphenyl taurate mmol/l 0.5 3-propynylaminoethyl imidazol mmol/l 0.01

Example 9 Potassium allyl phenyl taurate mmol/l" 0.1 2-propynyl-3-(beta hydroxyethyl) imidazol mmol/l 0.05 Sodium nonanoyl methyl taurate g./l 0.2

Example 10 Sodium isopropenyl taurate mimol/l" 0.3 2-popynyl-3-diethy-lenediamine irnidazol m:m-ol/l 0.08 Sodium octanoyll cyclopropyl taurate g./l 0.5

Example 11 Sodium l-butenyl taurate mmol/l 0.1 2-propenyl imidazol mmol/l 0.05

Example 12 2-butenyl tauric acid rnmol/l 2 p-toluene sul-fonamide g./l 10 Example 13 Sodium salt of l-butynyl amino propylene sulfonic acid mmoil/l 5 3-propynylaminoethyl imidazol =mrnol/l 1 Example 14 Sodium salt of Z-butynyl cyclopropylam-ino butyl-ene sulfonic acid mmol/l 10 o-Benzoyl sulfamide -g./l 5

Example 15 l-pentynyl phenylamino pentylene sulfonic acid mmol/l 5 2 propenyl im idazol mmol/l 0.001 Sodium formyl methyl taurate g./l 0.2

Example 16 Sodium acrylyl butyl taurate mmol/l 8 Benzene sulphonic acid g./l 1.5

Example 17 Sodium crotonyl propyl taurate mmol/l 10 Example 18 2-pentenoyl hexylarnino propylene sulfonic acid mmol/l 0.05 3-ipropynyl imidazo-l mml/l 0.001 Sodium oleoyl methyl taurate g./l 0.2

Example 19 Potassium vinylacetyl methyl taurate mmorl/l 1.0 Sodium saccharate 'g./l 1.5 Sodium octanoyl cyclo b utyl taur-ate (air agitation) 'g./l 0.5

Example 20 Sodium propiolyl pentyl taurate mmol/l 10 Sodium octanoylmethyl taurate g./l 0.2

Example 21 Sodium salt of butynoyl cyclobutylamino butylene sulfonic acid mmo1/L Example 22 Sodium hydroxy butynoyl ethylphenyl taurate mrnol/l 0.5 2-propynyl-3-(beta hydroxyethyl) imidazol mrnol/l 0.01 Sodium saccharate g./l 1.5 Potassium methyl glyoxyl taurate g./l 5

Example 23 Sodium pentynoyl hexyl taurate mmol/l 5 Z-butyne, 1,4-disulphonic acid g./l 1.5 Sodium butanoyl cyclopropyl taurate g./1 0.5

Example 24 Allyl methyl taurate mmol/l 1.0'

Sodium octanoylmethyl taurate (air agitation) g./l 0.2

6 Example 25 Sodium propargylmethyl taurate mmol/l 1.0 Sodium octanoylmethyl taurate (air agitation) mmol/l 0.2

Unless otherwise specified all parts and percentages in the specification and claims are by weight. The foregoing examples illustrate specific baths and processes, several being preferred. It is to be understood that the compositions and conditions can be varied. Therefore as many embodiments of this invention may be made without departing from the spirit and scope thereof and the invention includes all such modifications and variations as come within the scope of the appended claims.

What is claimed is:

1. An aqueous acidic bath solution for electroplating nickel containing at least one nickel salt as a source of nickel which plating solution includes a brightener having the structural formula wherein R is selected from the group consisting of alkenyl, alkynyl, alkenoyl and alkynoyl radicals having 1 to 6 carbon atoms; R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals; R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consisting of hydrogen and alkali metal.

Z. The nickel plating solution of claim 1 which includes a Wetting agent having the formula wherein R is an alkenoyl radical having 8 to 10 carbon atoms; R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals; R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consistnig of hydrogen and alkali metal.

3. The nickel plating solution of claim 1 which includes a sequestering agent having the formula Rrr- TI-RWSOSRN wherein R is an alkanoyl radical having 1 to 6 carbon atoms, R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals; R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consisting of hydrogen and alkali metal.

4. The nickel plating solution of claim 1 wherein the brightener is present in amounts of 0.1 to 10 mmol/l. of solution.

5. The nickel plating solution of claim 2 wherein the wetting agent is present in amounts of 0.5 to 5 g./l. of solution.

6. The nickel plating solution of claim 3 wherein the sequesteding agent is present in amounts of 0.1 to 5 g./l. of solution.

7. The nickel plating solution of claim 1 which includes sodium methyl oleoyl taurate.

8. An aqueous acidic bath solution for electroplating nickel containing at least one nickel salt as a source of nickel which plating solution includes a first brightener having the structural formula wherein R is selected from the group consisting of alkenyl, alkynyl, alkenoyl and alkynoyl radicals having 1 to 6 carbon atoms; R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals; R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consisting of hydrogen and alkali metal together with an aromatic sulfur compound as a second brightener of the first class.

9. The nickel plating solution of claim 8 which includes a wetting agent having the formula wherein R is an alkanoyl radical having 8 to carbon atoms; R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals; R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consisting of hydrogen and alkali metal.

10. The nickel plating solution of claim 8 which includes a sequestering agent having the formula wherein R is an alkanoyl radical having 1 to 6 carbon atoms, R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals, R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consisting of hydrogen and alkali metal.

11. A nickel plating solution of claim 8 wherein said first brightener is present in amounts of 0.1 to 10 mmol/l. of solution.

12. The nickel plating solution of claim 8 wherein said second brightener is present in amounts of 1 to g./l. of solution.

13. The nickel plating solution of claim 9 wherein the Wetting agent is present in amounts of 0.5 to 5 g./1. of solution.

14. The nickel plating solution of claim 10 wherein the sequestering agent is present in amounts of 0.1 to 5 g./l. of solution.

15. The nickel plating solution of claim 8 which includes sodium methyl oleoyl taurate.

16. An aqueous acid bath solution for electroplating nickel containing at least one nickel salt as a source of nickel which plating solution includes a first brightener having the structural formula wherein R is selected from the group consisting of alkenyl, alkynyl, alkenoyl and alkynoyl radicals having 1 to 6 carbon atoms; R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals, R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consisting of hydrogen and alkali metal together with, as a second brightener, an imidazol compound having the formula wherein R is selected from the group consisting of hydrogen and AR A being an aliphatic bridge and R being selected from the group consisting of unsaturated and saturated aliphatic and cyclic radicals and aromatic radicals; R and R1 being selected from the group consisting of hydrogen, aliphatic and cyclic, saturated and unsaturated hydrocarbon radicals; and wherein R is selected from the group consisting of hydrogen and --AR A being an aliphatic bridge and R being selected from the group consisting of aliphatic and cyclic, saturated and unsaturated hydrocarbon radicals and aliphatic radicals bearing at least one amino group and alkoxy groups; at least one of R and R being an unsaturated radical.

17. The nickel plating solution of claim 16 which includes as a third brightener of the first class an aromatic sulfur compound.

18. The nickel plating solution of claim 16 which includes a wetting agent having the formula wherein R is an alkanoyl radical having 8 to 10 carbon atoms; R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals; R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consisting of hydrogen and alkali metal.

19. The nickel plating solution of claim 16 which includes a sequestering agent having the formula R 5I lIRn S OGRtS wherein R is an alkanoyl radical having 1 to 6 carbon atoms, R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals; R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consisting of hydrogen and alkali metal.

20. The nickel plating solution of claim 16 wherein said first brightener is present in amounts of 0.05 to 5 mmol/l. of solution.

21. The nickel plating solution of claim 16 wherein said imidazol compound is present in amounts of 0.001 to 1 mrnol/l. of solution.

22. The nickel plating solution of claim 17 wherein said third brightener is present in amounts of 1 to 30 g./l. of solution.

23. The nickel plating solution of claim 13 wherein the wetting agent is present in amounts of 0.5 to 5 g./l. of solution.

24. The nickel plating solution of claim 19 wherein the sequestering agent is present in amounts of 0.1 to 5 g./l. of solution.

25. The nickel plating solution of claim 16 which includes sodium methyl oleoyl taurate.

26. The process of producing nickel deposits of improved ductility and corrosion resistance characteristics on a metal base which comprises electro-depositing nickel from an aqueous acidic bath by passing a current from an anode to a cathode to be plated, said acidic bath containing nickel in the form of a soluble inorganic salt, in the presence of a brightener having the structural formula wherein R is selected from the group consisting of alkenyl, alkynyl, alkenoyl and alkynoyl radicals having 1 to 6 carbon atoms; R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals; R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consisting of hydrogen and alkali metal.

27. The process of claim 26 wherein the brightener is present in amounts of 0.1 to 10 mmol/l. of solution.

28. The process of claim 26 wherein said bath includes as a second brightener an imidazol compound having the formula wherein R is selected from the group consisting of hydrogen and AR A being an aliphatic bridge and R being selected from the group consisting of unsaturated and saturated, aliphatic and cyclic radicals and aromatic radicals; R and R being selected from the group consisting of hydrogen, aliphatic and cyclic saturated and unsaturated hydrocarbon radicals; and wherein R is selected from the group consisting of hydrogen and AR A being an aliphatic bridge and R being selected from the group consisting of aliphatic and cyclic, saturated and unsaturated hydrocarbon radicals and aliphatic radicals bearing at least one amino group and alkoXy groups; at least one of R and R being an unsaturated radical.

29. The process of claim 28 wherein said first brightener is present in amounts of 0.05 to mmol/l. of solution and said second brightener is present in amounts of 0.001 to 1 rnrnol/l. of solution.

30. The process of claim 26 wherein said bath includes as a third brightener of the first class an aromatic sulfur compound present in amounts of 1 to 30 g./l. of solution.

31. The process of claim 26 wherein said bath includes a wetting agent having the formula wherein R is an alkanoyl radical having 8 to carbon atoms; R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals; R is an aliphatic bridge containing from 1 to 5 carbon atoms and R 14 is selected from the group consisting of hydrogen and alkali metal, said wetting agent being present in amounts of 0.5 to 5 g./l. of solution.

32. The process of claim 26 wherein said bath includes a sequestering agent having the formula R15 TlRr1SOaRm wherein R is a alkanoyl radical having 1 to 6 carbon atoms, R is selected from the group consisting of hydrogen, aliphatic, alicyclic and aromatic radicals; R is an aliphatic bridge containing from 1 to 5 carbon atoms and R is selected from the group consisting of hydrogen and alkali metal, said sequestering agent being present in amounts of 0.1 to 5 g./l. of solution.

References Cited by the Examiner UNITED STATES PATENTS 2,830,082 4/1958 Sexton et al. M 260-513 2,876,177 3/1959 Gundcl et al. 20449 3,006,822 10/1961 Todt 20449 3,084,187 4/1963 Gaertner 260513 3,130,135 4/1964 Ericson 204-49 3,133,006 5/1964 Ostrow et al 20449 JOHN H. MACK, Primary Examiner.

M. TILLMAN, G. KAPLAN, Assistant Examiners. 

1. AN AQUEOUS ACIDIC BATH SOLUTION FOR ELECTROPLATING NICKEL CONTAINING AT LEAST ONE NICKEL SALT AS A SOURCE OF NICKEL WHICH PLATING SOLUTION INCLUDES A BRIGHTENER HAVING THE STRUCTURAL FORMULA 